In today's market, polyurethane elastomers are utilized in a wide array of products and applications, including producing industrial coated fabrics. For these latter, the polyurethanes are generally linear polymers exhibiting elastomeric characteristics of high tensile strength and elongation.
These linear polyurethanes are quite varied in their final properties as a result of the large number of permutations that can be applied to the three main components that are used in their manufacture. These components are polyols, polyisocyanates, and one or more extenders (generally diols). Some examples of these compounds are: polyether, polyester, polycaprolactone, polycarbonate, and polybutadiene polyols; toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, naphthalene diisocyanate; xylene diisocyanate, hexane diisocyanate, and hydrogenated 4,4'-diphenylmethane diisocyanate; and 1,4-butanediol, 1,6-hexanediol, and 1,3-butanediol extenders.
Typically, polyurethane elastomers which are considered top of the line with respect to performance, include, for example, polytetramethylene glycol (polyether) polyurethanes and poly(butane adipates or hexane adipates) ester polyurethanes. Of these polymers, the polyether polyurethanes exhibit good hydrolytic stability and low temperature properties but are generally poor for fuel resistance and oxidation resistance, while the polyester polyurethanes are tough with good abrasion resistance, oxidation resistance and fuel resistance, but not particularly resistant to hydrolysis. Still, at the present time the polyesters are generally considered to represent the best compromise of physical properties and chemical resistance of the various polyurethanes.
There are also a few polyurethanes based on polycarbonate polyols in the market. It is well known that these polycarbonate polyurethanes have very good hydrolytic stability and generally have good to very good resistance to other degradation forces; however, they are usually too hard, rigid and brittle for use in industrial coated fabrics.
Currently, high performance coated fabrics are based on polyester polyurethanes in order to meet the specifications currently in effect, but resistance to hydrolysis remains their weak point and represents a problem for these products. Thus, there is a desire for improved hydrolytic stability in a number of applications. A polyurethane having improved hydrolytic properties and sufficient elastomeric character to be useful in the manufacturing of industrial coated fabrics is also desirable and needed.
It is known from Japanese Patent Specification Sho(61)-76275 that polyurethane elastomers can be produced from a diol mixture of a polyarbonate diol and a polyoxytetramethylene glycol, and/or a polydimethyl siloxane glycol; an organic diisocyanate and a chain extension compound. Practical Example 4 of Table I lists a porous polyurethane film formed from an 80/20 mixture of polycarbonate diol and polyoxytetra methylene glycol; 4,4'-diphenyl methane diisocyanate and 1,4-butylene glycol, while Practical Example 1 illustrates a film formed from a 50/25/25 mixture of polycarbonate diol/polyoxytetra methylene glycol/polydimethylsiloxane glycol; 4,4'-diphenyl methane diisocyanate and ethylene glycol. These porous films can be used in the manufacture of artificial leather or suede articles.
Also, Japanese Patent Specification Sho(61)-151235 discloses the preparation of aliphatic polycarbonate polyols from various mixtures of dialkyl carbonates and glycols. These polyols are described as having low color adhesion and smooth reactivity with isocyanates. Neither reference suggests that these materials can be used as or in the production of polyurethane elastomers for industrial coated fabrics.